Control apparatus



June 1, 1943. A. B. NEWTON CONTROL APPARATUS Filed Aug. 3, 1940 2Sheets-Sheet 1 Fig.4

INVENTORw Alwiru B. Newl'om BY I ATTORNEY UNITED STATES PATENT OFFICECONTROL APPARATUS Alwin B. Newton, Minneapolis, Minn, assignor toMinneapolis-Honeywell Regulator Company, Minneapolis, Minn, acorporation of Delaware Application August 3, 1940, Serial No. 350,298

7 Claims.

This invention relates to control apparatus wherein condition responsivedevices are employed to modulate a high frequency current.

An object of the invention is to provide a control system including acurrent responsive control device, and means to regulate the impedanceof an electrical winding in circuit with said control device inaccordance with the magnitude of a condition indicative of the need foroperation of m t l i 10 Hence, when a more sensitive device is required,

Another object of the invention is to provide a higher frequency may beemployed. such a control system having means to regulate In order toprovide a device responsive to the the sensitivity thereof. algebraicsum of two conditions, the air gaps ex- A further object of theinvention is to provide isting between the armature and the two endsmeans by which the operating range ofsuch a of the magnetic core aremade independently condition responsive system may be adjusted.variable. The length of one air gap is varied A still further object isto provide means for adin accordance with the magnitude of onecondijusting the operating range from a remote point. tion and thelength of the other air gap varied A further object oi the invention isto provide in accordance with the magnitude of the second means tomodify the action of such a system in condition. The reluctance of themagnetic ciraccordance with the magnitude of a second cult is then ameasure of the algebraic sum of condition. the two conditions.

A further object of the invention is the pro- The averaging ofaplurality of controlling convisiqn of a device which regulates theimpedance ditions may be obtained by connecting the wind of anelectrical winding in accordance with the g5 ings of a plurality of mycondition responsive dealgebraic sum of the magnitudes of a pluralityvices in series with a single source of energy and of conditions. asingle control device. The control device thus A further object of theinvention is to provide becomes responsive to the sum of the impedancesa system for operating a control device in acof the windings. Since thenumber oi! windings cordance with the average of the magnitudes of isconstant, the average impedance is directly a lurality of controllingconditions. proportional to the sum, and the control device A furtherobject of the invention is to provide responds, in eilect, to theaverage value of ima system for selectively operating one or more dance,of a plurality of control devices in accordance other objects andadvantages of the present inwith the magnitudes of one or morecontrolling vention willbe apparent from the following speciconditions,wherein the control devices are fication, claims, and drawings, ofwhich: located remotely from the condition responsive Figure 1 is asomewhat diagrammatic sketch devices, and are connected thereto by asingle f a, simple control system embodying my invenpair of conductors.tion, showing one form of my condition respon- I accomplish the objectsset forth by provid- 40 ive devices in cross section. ing an armaturewhich is positioned relative to Figure 21 a somewhat diagrammatic sketchof a magnetic core in accordance with the magnia different type ofcontrol system, showing in tude of a controlling condition. Thereluctance cross section other forms of my condition responoi the airgap between armature and core detersive device, mines the impedance ofan electrical winding i Figure 3 is a somewhat diagrammatic sketch ofwhich is wound around the core. An alternating a control systemutilizing a form of my condition potential of high frequency isimpressed across reSpOnSiVe device which esp to ctive this winding, andthe current flowingtheretemperature, the latter being shown mcrosssecthrough is employed to operate a current re- W and sponsive controldevice. Figures 4 and 5 are wiring diagrams of difierent The operatingrange of my condition responsive 33 of F systems embodying my .mvenmeans may be regulated by varying the normal In Figure 1 I have shown asystem wherein the air-gap length either by manually adjusting thepressure in a pipe is contmn d b v 81 H core or armature mounting means,or by passthe opening or which is new; g f' gf i ing a direct currentthrough a winding about the responsive device indicated generally at n.This magnet core, and thereby attracting the armadevice comprises acasing n which is separated ture closer to the core. If a oompensationofthe into upper and lower compartments by a ma action of my conditionresponsive means is dephragm II. The pressure in the pipe In i sired, itmay be secured by making the operating municated to the lowercompartment and serves to regulatethe position of the diaphragm II. Amagnetic core I5, about which is wound a coil I6, is supported withinthe upper compartment tending downward adjacent the diaphragm l4.

The bolt I1 is rotatable by a thumb piece l8 located at the outer endthereof and may be fastened in any desired position by means of a locknut I9. Rotation of the bolt |1 serves to change the position of theends of the core l5 with respect to the diaphragm H for purposes to bedescribed later. Rotation of the magnetic core IS on the bolt |1 may beprevented by any suitable means, not shown.

The coil I6 is connected in a circuit which includes a high frequencyoscillator and the input terminals of an amplifier 2|. The outputterminals of the amplifier 2| are connected to an ammeter or othersuitable indicating device 22 and to a solenoid 23. The oscillator 28and amplifier 2| are supplied with power through suitable connectionsfrom lines 24 and 25. The solenoid 23 is provided with a core 26 whichis attached to the valve I and regulates the oper-- ation thereof.

If the pressure in the pipe I8 falls below. the

value which it is desired to maintain, the diaphragm |4 falls slightly,moving away from the magnetic core l5 and thereby. decreasing theimpedance of the coil Hi. This allows a greater current to flow throughthe oscillator circuit to 7 output current flowing through the solenoid23 is correspondingly increased, thereby causing the solenoid core 26 tobe lifted, thus opening the valve I l to a greater extent. On the otherhand, if the pressure in the pipe l0 increases above the desired valuethe diaphragm l4 moves closer to the core l5, thereby increasing theimpedance of coil l6 and decreasing the current in the oscillator andamplifier circuits and allowing the valve to move toward its closedposition. It is therefore apparent that this system acts to regulate thepressure in the pipe Ill. The device may be adjusted to different valuesof pressure by tuming the thumb piece l8, thereby changing the normaldistance between diaphragm l4 and core. l5- and setting the normalcurrent through the solenoid 23.

Figure 2 In Figure 2 I have shown a temperature responsive controlsystem embodying my invention.

The condition responsive device of this system, which is adapted to beplaced in the room or space to be controlled, is shown generally at 21and comprises a casing 28 in which-is supported a magnetic core 29 and atemperature responsive member 30. The core 29 is supported by a washerfixed on a bolt 3| which is threaded through the top of casing 28 and isrotatable by means of a thumb piece 32. A locking nut 33 is provided tofasten the bolt in any desired position. On one leg of the core 29 iswound a coil 35 which is connected in circuit with a high frequencyoscillator 36 and a relay winding 31. On the other leg of core 29 is asecond coil 38 which is supplied with direct current from lines 39 and40. The amount of current supplied to the winding 38 is regulated byarheostat 4| whose movable contact 42 is positioned by a temperatureresponsive member 43.

The temperature responsive member comprises a sealed metallic chamberwhose upper the amplifier input terminals. The amplifier 41 on the legsthereof. An armature 48 is provided in the compensating device 44 forcooperation with the core 45. The armature 48 threadedly engages a shaft49 and is positioned relative to the core 45 by the rotation of saidshaft through means to be described later. Rotation of armature 48 withthe shaft 49 is prevented by pins 96 rigidly attached to the base ofsaid device 44 and extending upwardly through suitable apertures in thearmature. The winding 46 of the rebalancing device 44 is connected inseries with the winding of temperature responsive device 21. The winding41 of rebalancing device 44 is connected in parallel with the winding 38of the temperature responsive device 21. I

The relay winding 31 controls a switch arm 54 which moves between twocontacts 5| and 52 to control the operation of a reversible motorindicated generally at 53. I This motor 53 and the oscillator 36 areenergized from lines 54 and 55. When the switch arm 50 engages contact5| a circuit is completed from line 54 through a winding 56 of motor 53,contact 5|, and switch arm 50 to line 55. Energization of winding 58causes the motor to be rotated in a certain direc. tion which may be,for example, clockwise. When the switch arm 50 engages contact 52 acircuit is completed from line..54' through winding 51 of motor 53,contact 52, and switch arm 58 to line 55. This winding operates to turnthe motor in the opposite or counterclockwise direction. The motor 53drives, through a reduction gear mechanism indicated schematically at58, a beveled gear 59 which cooperates with a beveled gear 68 on theshaft 49. The motor 53 also drives, through a shaft 6| connected to thegear reducing mechanism 58, a pinion 62 which is in engagement with arack 63 for operating a valve 64. The valve 64 controls the supply ofheating fiuid, for example, steam, to the room or space in which thetemperature responsive device 21 is located.

When the temperature of the room or space being controlled falls belowthe desired value the vapor pressure in the chamber 30 is reduced andthe armature 34 moves away from the core 29.

This results in a decrease in the impedance of coil 35 and a consequentincrease in the current flowing through the circuit thereof, whichincludes the relay winding 31. The switch arm 50 is thereby moved intoengagement with the contact 52 thus energizing the winding 51 andcausing rotation of motor 53. The direction of rotation of motor 53 issuch as to open valve 64 thus increasing the supply of heat to the spacebeing controlled. At the same time the shaft 49 is turned in suchadirection as to move armature 48 closer to core thereby increasing theimpedance of winding 46. Th s action continues until the increase in theimpedance of winding 46 has balanced the decrease in the impedance ofwinding 35 and thereby reduced the flow-of current through the relaywinding 31 to its normal value. The switch arm 58 is biased so that withcontrol.

- the bolt 10.

normal current flowing through relay winding 3? the switch arm engagesneither contact 55 nor 52.

If the temperature in the room or space being controlled rises above itspredetermined value, armature 34 moves closer to core 29, increasing theimpedance of winding 35, and decreasing the current through relaywinding 31, thereby switch arm 58 to engage contact 59. This completesthe energizing circuit for winding 56 of motor 53 which operates toclose the valve 6% and to move armature 48 away from core 45. Thisaction continues until the decrease in the impedance of winding 48balances the increase in the impedance of winding 35.

The temperature responsive device ii; may be p room or space undercontrol when the outdoor temperature falls. Such a fall in temperaturecauses the contact arm 42 to move as indicated by the legend in thedrawing, counter-clockwise across the rheostat it thus increasing theresistance in the circuit of windings 3ii'and til and decreasing thecurrent flow through those windings. This results in a decrease in themagnetic consequent decrease in the impedance of coiis 35 and 36. Theflux decrease aiso reduces the attractive force between core 229 andarmature at, which thereupon moves slightiy away from core 29, producinga further decrease in the impedance of coil 35. It is therefore apparentthat a drop in outdoor temperature produces an effect on the systemsimilar to that produced by a drop in temperature within the room orspace under An increase in the outside temperature likewise produces anefiect which simulates an increase in the temperature of the room beingcontrolled. The normal temperature which the system is to maintain maybe set by means of the thumb screw 32.

Figure 3 bolt 18 which passes through the top of the housing 61. Theposition of the core 68 within the housing 61 may be varied by means ofthe thumb piece H and locking nut 12 which engage Two brackets 13 and 14are adjustably mounted within the housing 61 by bolts 18 and I9 threadedthrough the base plate 68 and the brackets I3 and I4, respectively. Thebrackets I3 and I4 are of magnetic material, and have slidable matingsurfaces, as at I20, which are so proportioned as to engage each other,at least partially, even under extreme conditions of relative adjustmentof th'ebrackets. A spring steel bar is attached at one end to thebracket I3 so that its free end is adjacent one end of the core 89. Aweb or other humidity responsive means I8 is stretched between the freeend of bar I! and the lower part of the bracket 13. As the humidity ofthe space in which the device is placed increases, the web becomesslack, allowflux passing through the cores 29 and $52, with a ing thefree end of the bar it to move toward the adjacent end of the core 69. Atemperature responsive member ll, shown as a bimetallic strip, issupported at one end by the bracket it and has its other end normallypositioned near the other end of the core is. An increase in thetemperature to which the strip ll is exposed will cause it to warpmoving its free end nearer the core 69. The path of the magnetic fluxwhich passes through the core 59 may be traced from one end of the core69 across the air gap to the bar 15, through the bracket 13, the mat ingsurfaces at I20, bracket M, bimetallic member 71 and'across the air gapto the other end of the core 66. It may therefore be seen that the totallength of the air gaps in this magnetic circuit is proportional to thesum of the two conditions which determine the effective temperature,namely, the temperature and the hu midity. The length of these air gapsregulates the impedance of a coil around one ieg the core 69. This coil88 is connected in series with a high frequency oscillator tit and asolenoid Bl controlling a switch The motor 65 and the oscillator 93 aresupplied with power from lines and motor circuit may be traced from line55d, through switch arm 82, contact 553, and motor to line i When theeffective temperature oi the space being controlled increases above thevalue it is desired to maintain, the impedance of the coil 88 isincreased, due to the movement of the condition responsive members 15and H. This decreases the current flow through the solenoid 8i andallows the switch arm 82 which is suitably biased to drop against thecontact 83 thereby completing a circuit through the motor 65. Operationof the motor actuates the air conditioning system to reduce theeffective temperature, whereupon the system energizes the solenoid 8iand the motor circuit is again opened.

The thumb screw "II and the associated lock nut I! serve to adjust thetemperature and humidity responsive devices simultaneously. A similarthumb screw 84 and lock nut 85 are provided on the bolt 18 so that thehumidity responsive member 18 may be adjusted independently. Anotherthumb screw 88 and lock nut 81 are provided on the bolt I9 forindependent adjustment of the temperature responsive member H.

In addition to these means for manually changing the adjustment of thedevice means are provided for adjustment of both the temperature andhumidity responsive members from a plurality of remote locations. Onemeans for remote adjustment comprises a coil 88 wound about the core 69.The amount of current flow through this coil is determined by a rheostat88 which may be located at a remote-point. A change in the currentflowing through this circuit serves to change the magnetic flux throughthe core 69 and thereby changes the impedance of coil 80 and theattractive force between corc 69 and the-condition responsive members 15and 11. A second means for remote adjustment comprises a rheostat 92similar to rheostat 89 and connected to the coil 88 so as to superimposea direct current upon the high frequency current supplied thereto by theoscillator 93. The eifect of the direct current in the coil 80 issimilar to that of the current in the coil 88. These circuits aresupplied with direct current from lines 80 and 9|.

It will be apparent to those skilled in the art that the compensatingrheostat H of Figure 2, and that the adjusting rheostats 89 and 92 ofFigure 3 are substantial equivalents, and that.

Figure 4 I have illustrated in Figure 4 a system where 'in a pluralityof condition responsivev devices are used to control a valve H5 inaccordance with the average magnitude of the conditions measured. Twocondition responsive devices which are shown schematically at I and MI,may be of any of the types'shown in Figures 1, 2, and 3. For example,they may be temperature responsive. devices in a system wherein one suchdevice is placed in each room of a building, and the average roomtemperature measured thereby is utilized to control the opening of thevalve H6 in the main eteam line of a boiler; Such a system is used tokeep the steam line pressure just high enough to supply the demand forheat, so as to avoid the waste resulting from unnecessarily high steamline pressures. this system, so that the opening of the valve I ischanged proportionally to a change in the average temperature.

The condition responsive devices I00 and IM are provided with variableimpedance windings which are connected in a series circuit with a highfrequency oscillator I02 and a relay winding I03.

through a conductor 91, relay winding I03, a conductor 96, the coil ofcondition responsive device IOI, a conductor $9, and the coil ofcondition responsive device I00, back to oscillator I02. The relaywinding I03 operates a switch arm I 04 between contacts I05 and I06against suitable biasing means. Contacts I05 and I06 are mounted on acarriage I 01, of insulating material, which moves along a threadedshaft I08 in accordance with the rotation thereof. shaft I08 is rotatedby a reversible motor I09 through a suitable gear reduction mechanismshown diagrammatically at IIO. Motor I09 is provided with two windingsIII and H2, which may be selectively energized to drive the motor ineither direction. The motor I 09 also drives, through a suitableconnection with the gear reductlon mechanism I I0, a pinion II3 whichcooperates with a rack II4 to position the valve I I5.

The motor windings I II and H2 and the oscillator I02 are supplied withenergy from lines II 6 and III. The circuit for energizing winding IIImay be traced from line II6, through a conductor H8, winding I I I,contact I06, and switch arm I04 to line Ill. The circuit for energizingwinding II2 may be traced from line I I6 through conductor 8, windingII2, contact I05, and switch arm I04 to line I".

A follow-up action is provided in This circuit, hereinafter termed therelay circuit, may be traced from oscillator I02 The- nected to thecontrol devices through one pair 7 The current flowing through the relaycircuit is inversely proportional to the sum of the impedances of thecoils in the devices I00 and I 0|. Since the number of coils is constantfor any given system, this current may be usedv as a measure of theaverage value of the temperatures to which the devices I00 and IOI areexposed.. I

When the average temperature falls below thevalue which the system isadjusted to main-- 7 spective radiators I30, I3I, and I32.

tain, a decrease in the impedance of the relay circuit results, with aconsequent increase in the so as to open valve H5, and shaft I03 isrotated so as to drive carriage I01 to the right. This action continuesuntil carriage I01 is driven far enough to separate contact I06 fromswitch arm I04.

On the other hand, if'the average temperature rises above the desiredvalue, the relay circuit impedance is increased, and the current flowingtherethrough is decreased. This weakens the attractive force of relaywinding I03, and the biasing means becomes effective to move switch armI04 against contact I05, thereby completing the energizing circuit formotor winding II2. Energization of winding II2 causes rotation of motorI09 in such a direction that pinion H3 is rotated so as to close valveIII. and shaft I00 is rotated so as to drive carriage I01 to the left.This action continues until contact I05 is separated from switch armI04.

' It should be apparent to those skilled in the art, in view of theforegoing description, that the switch arm I04 is positioned inaccordance with the average temperature measured by the devices I00 andMI. That is to say, for any value of average temperature within theoperating range of the system, the switch arm I 04 is moved to adefinite position. By virtue of the follow-up mechanism operated by themotor I09, the valve I I5 follows the motion of switch arm I04,, so thatthe valve, also, is positioned in accordance with the averagetemperature.

The position of the valve II5 for any given value of average temperaturemay be changed by adjusting the thumb piece on-the condition responsivedevices I00 and IOI. Remote adjustment of the valve position isaccomplished by means of a rheostat II 9 through which direct current issupplied to the, relay circuit. The

operation of this rheostat is similar to that of I In Figure 5 I haveshown a system wherein a plurality of condition responsive devices arelocated remotely from a plurality of devices to be selectivelycontrolled thereby and wherein all the condition responsive devices areconof conductors.

The condition responsive devices are shown diagrammatically in Figure 5as three magnetic cores I2I, I22. and I 23 provided with coils numberedI24, I25, and I26, respectively. Each coil is connected through aband-pass filter shown diagrammatically in the drawing at I21 to a pairof conductors I28 and I29. The condition responsive devices are locatedin separate heating zones to which heat is supplied by the re- Thesupply of steam to these radiators is controlled by valves I33, I34, andI35, respectively. Each of these valves is connected in a branch steamline between its associated radiator and a main steam line I36. Thesevalves are preferably of the solenoid operated type and each solenoid isconnected in series with a high frequency oscillator I31 and with theinput terminals of a band-pass filter I38. The frequency of each of theoscillators is adjusted at a different value and the band-pass filterassociated with each oscillator is designed to pass only current of thatfrequency. Similarly the band-pass filter i2! associated with eachcondition responsive device is designed to pass only current of thefrequency associated with the corresponding control device. It maytherefore be seen that each condition responsive device may operate itsown particular control device without interference from any of the othercondition responsive devices and that by using this system it is onlynecessary to use one pair of conductors between the group of conditionresponsive devices and the group of control devices.

While I have shown several specific embodiments of my invention it willbe understood that this is for purposes of illustration only and that myinvention is to be limited only by the scope of the appended claims.

I claim as my invention:

1. A system for operating a control device including in combination, asource of alternating electrical energy, an impedance having a core ofmagnetic material and a coil about said core, an armature cooperatingwith said core, means for regulating the distance between said annatureand said core in accordance with the magnitude of a condition indicativeof the need for operation of said control device, a connection betweensaid source of energy and said control device including saidcoil, asource of direct current connected to said coil, and means forcontrolling the flow of direct current through said coil.

2. A system for operating a control device including in combination, asource of alternating electrical energy, an impedance having a core ofmagnetic material and a coil about said core, an armature cooperatingwith said core, means for regulating the distance between said armatureand said core in accordance with the magnitude of a condition indicativeof the need for operation of said control device, a connection betweensaid source of energy and said control device including said coil, asecond coil about said core, a source of direct current connected tosaid second coil, and means for controlling the flow of direct currentthrough said second coil.

3. A system for operating a control device including in combination, asource of alternating electrical energy, an impedance having a core ofmagnetic material and a coil about said core, an armature cooperatingwith said core, means for regulating the distance between said armatureand said core inaccordance with the magnitude of a condition indicativeof the need for operation of said control device, a connection betweensaid source of energy and said control device including said coil, asource of direct current, a connection between said coil and saiddirect. current source, means for controlling the flow of currentthrough said connection, a second coil about said core, a connectionbetween said second coil and said direct current source, and means forcontrolling the flow of current through said last mentioned connection.

4. A system for operating a current responsive control device inaccordance with the effective temperature of a space to be controlled,including in combination, a source of alternating electrical energy, animpedance having a core of magnetic material and a coil about said core,an armature having its ends adjacent the ends of said core, means forregulating the distance between one end of said armature and theadjacent core end in accordance with the temperature of the space to becontrolled, means for regulating the distance between the other end ofsaid armature and the corresponding core end in accordance with thehumidity of the space to be controlled and a connection between saidsource of energy and said control device including said coil.

5. A system for operating a current responsive control device includingin combination, an oscillator for providing alternating electricalenergy of high frequency, an impedance having a core of magneticmaterial and a coil about said core, an armature cooperating with saidcore, means for regulating the distance between said armature and saidcore in accordance with the magnitude of a condition indicative of theneed for operation of said control device, a circuit path for the outputof said oscillator including said coil and said control device, andmeans'for varying the saturation of said core independently of themagnitude of said condition.

6. A system for operating a current responsive control device includingin combination, an oscillator for providing'alternating electricalenergy of high frequency, an impedance having a core of magneticmaterial and a coil about said core, an armature cooperating with saidcore, means for regulating the distance between said armature and saidcore in accordance with the magnitude of a condition. indicative of theneed for operation of said control device, a circuit path for the outputof said oscillator including said coil and said control device, wherebyvariations in the impedance of said coil cause operation of said controldevice, and means operated concurrently with said control device forvarying the impedance of said circuit in a sense opposite to that of thevariations causing operation of said control device.

7. A system for modulatingly positioning a control device in accordancewith the value of a variable condition, comprising in combination, asource of alternating electrical energy, first variable impedance meansincluding a core of magnetic material, a coil wound on said core, anarmature cooperating with said core, and means for regulating thedistance between said armature and said core in accordance with saidvariable condition, circuit means including said source and said firstvariable impedance means, a motor for driving said control device, meansresponsive to an electrical current flowing in said circuit means forcontrolling said motor, second variable impedance means in said circuit,and a connection between said motor and said second variable impedancemeans for yarying saidsecond impedance means in a sense opposite to thatof the variation of said first impedance means which caused operation ofsaid motor,

ALWIN B. NEWTON.

